I noticed a folder on my Laptop

Now I had mentioned that the laptop was 2nd hand. Usually, people were careful and cleaned the hard drive before selling it on. I went to do a factory reset just if anything dodgy had been left on the system when I noticed a folder hidden away. It was simply titled 'CB'. Normally I would have just proceeded with the reset and ignored it, but I was bored with not much to do, so my curiosity got the better of me. I opened a folder and found myself faced with another set of folders. Some of these seemed to have usernames of some sort, other folders I couldn't work out what they were yet.